A redundant array of independent disks (RAID) group includes multiple disks for storing data. For RAID Level 5, storage processing circuitry stripes data and parity across the disks of the RAID group in a distributed manner.
In one conventional RAID Level 5 implementation, the storage processing circuitry brings offline any failing disks that encounter a predefined number of media errors. Once the storage processing circuitry brings a failing disk offline, the storage processing circuitry is able to reconstruct the data and parity on that disk from the remaining disks (e.g., via logical XOR operations).
Unfortunately, there are deficiencies to the above-described conventional RAID Level 5 implementation in which the storage processing circuitry brings offline any failing disks that encounter a predefined number of media errors. For example, once the failing disk is brought offline, the entire RAID group is now in a vulnerable degraded state which is easily susceptible to unavailability. In particular, if a second disk encounters the predefined number of media errors, the storage processing circuitry will bring the second disk offline thus making the entire RAID group unavailable.
As another example, before a failing disk reaches the predefined number of media errors, suppose that the storage processing circuitry starts a proactive copy process to proactively copy data and parity from the failing disk to a backup disk in an attempt to avoid or minimize data and parity reconstruction. In this situation, the proactive copy process may actually increase the number of media errors encountered by the failing disk due to the additional copy operations caused by the proactive copy process. Accordingly, the proactive copy process may actually promote or cause the storage processing circuitry to bring the failing disk offline sooner.